It is generally customary to journal blanket cylinder and plate cylinder eccentrically to adjust the printing pressure. The printing pressure of the plate cylinder to blanket cylinder respectively of the blanket cylinder to the impression cylinder can be set by eccentric journals. To obtain this, the plate cylinder and blanket cylinder, which touches the impression cylinder in the basic printing position, are positioned so that the axes of the plate cylinder, the blanket cylinder and the eccentric blanket cylinder journal are positioned on one first straight-line. The axes of the plate cylinder and eccentric plate cylinder journal are on a second straight-line, which is perpendicular to the first straight-line.
The blanket cylinder is swiveled around the axis of the corresponding eccentric journal depending on the material thickness of the processed printing material, so that the blanket cylinder is moved away from the impression cylinder and the printing pressure between both cylinders is adjusted accordingly. This swiveling of blanket cylinder around the axis of the eccentric journal also causes a distancing of the blanket cylinder from the plate cylinder. Therefore the plate cylinder must be tracked to the blanket cylinder by rotating the plate cylinder around axis of the eccentric plate cylinder journal. This always assures the same distances between the axis of blanket cylinder and plate cylinder although the distance between blanket cylinder and impression cylinder is changed depending on the processed printing material.
For example, German patent No. 4,142,755 describes apparatus for the synchronous, simultaneous adjustment of the cylinders to each other by an adjustment drive for each plate cylinder and blanket cylinder and to couple both adjustment drives so that a simultaneous tracking of the plate cylinder to the blanket cylinder is made, depending on the position of the blanket cylinder relative to the printing cylinder. A disadvantage of that apparatus is the required cost of the drive system and of its manufacture.